1. Technical Field
The present invention relates to an improved method for processing dough to form a rice crisp with visual inclusions. More specifically, this invention relates to a rice-flour-based dough formulation that allows the dough to be processed on tortilla sheeting equipment.
2. Description of Related Art
Rice snacks are well-known in the art. These snacks are very popular in Japan and have become increasingly popular in the United States because of their nutritional appeal. Additionally, rice snacks with visual inclusions are becoming increasingly popular for the same reason. The visual inclusions consist of whole pieces of rice or grain that are imbedded in the cake and that are visible within and on the snack. Health-conscious consumers are expressing a greater demand for rice-based snacks, especially alternatives to the more traditional puffed rice cake, such as rice crisps and/or rice chips. Thus, there is a need for expanding the available methods for producing rice-based snacks.
There are many drawbacks associated with the traditional method of manufacture. The first drawback is the high cost associated with the production equipment an operation. For example, the equipment used to form a traditional rice cake must be capable of precise and timed expansion as well as being able to heat its contents to high temperatures at high pressures. Yet another drawback is that the traditional method of manufacture is very time intensive. Each cake manufactured must go through the lengthy compression and heating stages which reduce total throughput. Finally, the high temperatures and pressures of the traditional process limit the amount of visual inclusions that can be included in the rice cake, as the high temperatures and pressures are very degrading.
There have been many different methods proposed for making rice snacks with visual inclusions. Note, however, that such prior art methods typically relate to puffed-rice cakes, rather than sheeted-dough-derived rice crisps or chips. For example, U.S. Pat. No. 5,871,793 provides a method wherein pre-puffed rice is coated with a binder agent such as a water-based mixture and heated with ultrasound energy until bonded. This overcomes the high temperatures and pressures associated with traditional methods that limit the amount of visual inclusions in the cake.
Because of the high capital costs associated with the production of rice snacks, there exists a need for a novel method that allows for the production of rice snacks on cheaper or more readily available equipment. An alternative method for producing rice snacks is by using existing tortilla sheeting equipment for processing and sheeting rice-based dough.
Tortilla sheeters, hereinafter “sheeters,” typically comprise two or more rollers. Sheeters can vary in size and can be as large as, or larger than, about 9 feet in length. One or more pairs of rollers are spaced apart to form a gap between the rollers called a nip size. The thickness of the dough can be adjusted by adjusting the nip size. The two rollers rotate in opposite directions, and the dough passes through the gap. The dough is then collected by a third roller or by a conveyor that transports the sheeted dough for subsequent processing, i.e. cutting, puffing, frying, baking, etc. A stripping wire or peeling wire is often held across one of the rollers (the roller upon which the dough adheres immediately after passing through the gap area) to help dislodge the dough or dough pieces from the roller.
Many factors can affect the consistency of a dough sheet operation. These include, but are not limited to, amount and type of each ingredient, ingredient distribution within the dough, water content, nip size, the speed of the rollers, and the energy absorbed by the dough from the rollers. Downstream processing such as cutting, frying, etc, as well as the final product quality is likewise dependent on dough sheet properties being precisely controlled. An inconsistent sheet thickness or size can result in erratic product taste, texture or appearance. Thus, to consistently produce a quality product, the sheeting operation must yield dough sheets of consistent size and thickness.
There are many problems with using corn masa sheeters in the processing of a rice-water dough to manufacture rice or grain cakes with visual inclusions. Most of these problems arise from the interaction and competing nature of three important properties of the rice-water mixture that forms the dough: 1) adhesiveness, 2) cohesiveness, and 3) viscosity or viscoelasticity, depending on the liquid-like and/or solid-like nature of the dough (for example, if the dough is liquid-like, its viscosity will be physical property of interest; if the dough is more solid-like or polymer-like, its viscoelasticity will be the physical property of interest). The dough, for example, must be viscous enough to form tightly-bonded dough. If the dough's viscoelasticity, on the other hand, is too low, the resulting product will have a compromised texture (the product could, for example be too hard, too thin, and/or too glossy). If the viscoelasticity, however, is too high, the rice dough will resist the sheeting pressures, increase the mechanical stress, and increase the risk of mechanical failure. For example, possible mechanical issues might include: breaking the peeling wire; stalling, overheating, and/or tripping the driving motors; buckling of the dough before the rollers; buckling of the rollers; increasing the shear stress and/or or work input to the dough beyond the intended amount. Undesired or unanticipated increases in shear stress and/or work input to the dough could potentially be catastrophic to the final product, as well as to the machinery, as differential sheeting equipment is generally designed for relatively low shear stress. Because some tortilla rollers are as large as, or larger than, 9 feet in length, the buckling resulting from highly-viscoelastic dough can be severe. Additionally, as discussed above, other processing operations as well as the final product are dependent on uniform sheeting. Buckling results in a non-uniform sheet which creates processing problems as well as variability in final product attributes.
A large viscoelasticity in dough could normally be overcome by supplying additional power to the rollers to limit the buckling. However, this option is not available when producing rice cakes with visual inclusions. The inclusions provide an upper limit on the power supplied to the sheeter rollers; too much power will result in breaking the intact rice grains that make up the visual inclusions.
Similar to the dough's viscosity and viscoelasticity requirements, the rice dough must be cohesive and adhesive enough to form a dough. However, prior art rice dough that is cohesive enough and adhesive enough to properly form a dough will usually be too adhesive for processing and will adhere to the surface of the rollers, causing jams, undesirably-rough surface, or tears in the sheeted dough.
Finally, another problem that arises is that water content cannot be adjusted to control water dependent processing variables because the water content is determined by the target dough rheology. For example, the dough must be cohesive enough to support the visual inclusions within the dough, while the viscoelasticity of the dough must be tightly controlled to minimize buckling of the rollers. Because cohesiveness and viscoelasticity are both functions of water content, the target viscoelasticity and target cohesiveness of the dough are achieved by adjusting the water content of the water-rice dough. Once water content is set to yield a desired rheology, it cannot, without the teachings of the present invention, be independently controlled to affect other processing results that are likewise factors of water content such as oil take-up and expansion of the visual inclusions. Thus, the viscoelasticity, adhesiveness, and cohesiveness of the rice-water mixture are so coupled that none can be advantageously compromised enough to make the dough suitable for processing on existing tortilla sheeters. Consequently, there is a need to decouple the viscoelasticity, adhesiveness, and cohesiveness of the rice-water mixture to allow the dough to be processed on tortilla sheeters without compromising final product quality.